The Cenozoic Era in Australia

Cenozoic era starts with the extiniction of dinosaurs 65 million years
ago.

Although the first
mammals evolved not long after dinosaurs in the end of Triassic period,
mammals were small and unable to compete with the successful dinosaurs
during the Mesozoic Era.

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Now that the dinosaurs
were extinct, mammals got
the chance and started evolving into many different species including
large animals. The Eocene Epoch saw the first whales
and primates. Then there were some cold times with ice ages during
Oligocene, Miocene and Pliocene. Homo Erectus and Homo Habilis evolved
in the late Pliocene, while Neanderthals and Homo sapiens evolved in
the end of Pleistocene.

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Australia during the Cenozoic Era
For Australia, the extinction
of dinosaurs
roughly coincided with the final breakup of Gondwanaland,
when
Australia and Antarctica separated from each other and Australia
finally got the shape it has today.

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Australia is a Moist
Continent
Antarctica was not covered in ice, and Australia was a much moister
continent than it is today. It was covered in tropical
rainforests, remaining pockets of which
can still be seen in Daintree
in north Queensland, Finke
Gorge in Northern Territory, and Carnarvon
Gorge in central Queensland, amongst
others.

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Australian Continent Dries
But about 30 million years ago, Australia had drifted far enough away
from Antarctica that a complete circumpolar current could form around
Antarctica. First that current was reasonably warm, and both continents
still supported temperate
rainforests.
About 15 million years ago however, the temperatures got cooler and
Antarctica developed glacial conditions. As the ice cover growed on
Antarctica, Australia got drier, partly because of the amount of water
that is tied up in glaciers. The drying
of Australia has been going on, with small
exceptions, until today, when 2/3 of Australian continent is covered in
deserts
and semi-deserts.

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The Oldest Mammal Fossils in Australia
Some of the oldest animal fossils found in Australia are these of platypus
- the monotreme
mammal that has apparently been living here continuously for 110
million years (way back into the age of dinosaurs!). The oldest bird
fossil is a 115 million years old feather, and the oldest frog fossil
dates back to 54.5 million years.

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Megafauna of the Cenozoic Era
As in many other parts of the world, some species of Australian mammals
developed into very large animals. Such "megafauna" evolved in
Australia about 1 million years ago, and included giant kangaroos,
echidnas,
wombats,
3m-high emus,
7m-long goannas and some species with no
living relatives such as diprotodons, palochesters, and carnivorous
marsupial lions
that could climb trees. All these megafauna got quite suddenly extinct
in Australia about 46,000 years ago. A hotspot for megafauna fossils is
the Riversleigh fossil field in Lawn
Hill National Park in north-western
Queensland.

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